Process of making nitrated carbohydrates.



irnn STATES Patented. May 23, 1 905.

" ATENT @rricn.

ARTHUR HOIIGH, OF DOVER, NEi/V JERSEY.

SPECIFICATION forming part of Letters Patent No. 790,840, dated May 23, 1905. Application filed June 13, 1903- Serial No. 161,371.

.To all whom it vnay concern:

Be it known that I, ARTHUR HOUGH, a subject of the King of Great Britain, residing in Dover, Morris county, New Jersey, have invented some new and useful Improvements in Processes of Making Nitrated Carbohydrates, of which the following is a specification.

My invention relates to the manufacture of nitrated carbohydrates used as explosives, and has for its object to provide an eflicient process for the economical manufacture of a compound which will be superior in stability and in explosive power to analogous bodies hitherto produced.

Nitrated compounds have been made from starch in various manners by treatment with nitric acid to which sulfuric acid is generally added. It has been found, however, that the highest nitrate obtainable was the hexanitrate, and even this has been obtained in a rather inefficient way, since it has always appeared mixed with tetranitrate and trinitrate, which lower nitrates had to be removed. The main reason for the inefiiciency of earlier processes is found, in my opinion, in the presence of too large a quantity of water at the beginning of the process and, further, in the fact that a considerable dilution of the acids takes place during the nitration, owing to the formation of water. Furthermore, it has been proved that when a carbohydrate has once been nitrated ever so little an increase of the degree of nitration can be obtained only with the greatest difficulty. For this reason whatever degree of nitration is desired must be edected at the moment the carbohydrate comes into contact with the acids for the first time.

I have secured very superior results by the process hereinafter described, in'which acids of great strength are employed and in which the strength of the acid is preserved during the whole step of nitration. ploy an excess of free sulfuric anhydrid at the beginning of the nitration and make provision for adding anhydrid to preserve such excess during the entire step'of nitration. I have found that by thus proceeding I obtain a body containing sixteen and a half per cent. of nitrogen, which would indicate that this product is an octonitrate of starch. So far Preferably I emas I am aware a nitrate higher than the hexanitrate has never been produced from starch prior to my invention. My process is also remarkable for its efficiency in that I obtain almost pure octonitrate with a very small proportion of lower nitrates admixed, which lower nitrates are readily removed by the stabilizing process.

In detail I proceed as follows: As raw material I employ corn-starch, which should not contain any alkali, as this will seriously interfere with nitration. I therefore prefer to employ starch say corn-starch w extracted from the natural material by means of sulfurous acid or water. Starch extracted by the alkali process is also available, but should first be carefully treated to remove all traces of alkali. I first dry the starch carefully. The temperature should not be too high or the starch will burn. I find that a temperature of about 275 Fahrenheit is well adapted for the purpose, and the best way of drying is by means of steam heat. The moisture is preferably taken away by suction, and it is advisable to constantly agitate the starch while it is being dried. Commercial cornstarch contains from seven per cent. to ten per cent. of moisture, and when dried as above described the moisture may be brought down to .01 per cent. The starch is allowed to cool to the temperature of the surrounding air, or about Fahrenheit, and is then ready to be nitrated. v t

For the purpose of nitration I employ a mixture of acids of about the following constitution: three parts, by weight, of nitric acid (HNO3) of about ninety-five per cent. monohydrate and containing as low a percentage of lower oxids of nitrogen as possible, and two parts, by weight, of sulfuric acid of about ninety-eight per cent, and to this mixture I add enough Nordhausen sulfuric acid containing about forty per cent. of free S03 to bring the HNOs and HZSOi to one hundred per cent. concentration and allowing from one to two per cent. of free SO; in the solution. The mixture is well stirred, so as to render it homogeneous and is allowed to cool to about from 50 to Fahrenheit. The presence of free sulfuric anhydrid is of great value in insuring a very high yield of the new compound.

Into the acid mixture above described I introduce the dried starch. The introduction should be effected in such a manner as to avoid the floating of the starch on the surface, and for this reason I forcibly inject the finely-powdered starch, so as to throw it beneath the surface of the acid mixture. If the starch were allowed to float, the dry portion would be acted upon by the nitric-acid vapors, producing a low nitrate which I desire to avoid.

At the same time that the dry starch is introduced into the mixed acids I inject an amount of sulfuric acid having an excess of free sulfuric anhydrid, preferably sufi icient to keep the acids mixture at all times at leastat the maximum concentration of one hundred per cent. :EINOB and one hundred per cent. H2 S04. Preferably, however, the presence of free sulfuricanhydrid should be preserved in about the proportion of two per cent. Too great an excess of anhydrid will lead to the formation of sulfo compounds and interfere with the nitration. I find that at a temperature of 50 Fahrenheit the starch requires about ten minutes contact with the acid mixture to bring about a practically complete nitration to the eighth degree, so that the flow of sulfuric acid containing free sulfuric anhydrid must be regulated to absorb the water liberated from the starch during this time. Should the temperature of the mixture rise, the action is more violent,and the flow of the reinforcing acid must be accelerated. The temperature should not fall below 45 When proceeding at 50 Fahrenheit, the product is almost wholly octonitrate with a small percentage of hexanitrate.

It is of great importance for the securing of perfect results that the temperature should be kept as uniform as possible during nitration. Furthermore, it is preferable that the density of the acid mixture should be kept practically constant, for if at any time the strength of the acid is reduced beyond a certain point no octonitrate will be formed. I have also found that if the HNO3 and HQSOi should at any time fall below the full concentration of one hundred per cent. this will lead to a material increase in the proportion of the hexanitrate which is formed as an impurity. For this reason it is advisable to always preserve an excess of free sulfuric anhydrid, so as to be sure that the acids will never fall below the full concentration. If the vessel within which nitration is conducted consists of iron, the excess of free sulfuric anhydrid should preferably not rise above three per cent. in order to avoid attack of the iron by the acid.

hen the operation of nitrating has been completed, the nitrated carbohydrate is separated from the excess of acids in any suitable manner, as by filtration. The acid thus removed may be rendered serviceable for an other operation by adding an amount of HNO3 corresponding to that taken up by the starch. As there is a constant formation of H2801 by the combining of free sulfuric anhydrid with the water liberated from the starch, the nitric acid may be removed by distillation when the amount of sulfuric acid has become excessive.

When the nitrated product has been removed from the adhering acids, it is first washed and then stabilizedthat is, freed from admixed lower nitrate. The washing is done by first treating the nitrated starch with plenty of water, agitating it well, and removing any free acid left by the addition of an alkali-for instance, sodium carbonate. The product is then brought into a filter-press and formed into cakes, which may be then removed and broken up for the stabilizing treatment or the explosive may be stabilized in the press. The stabilizing must of course be eifected by means of an agent that will have no action on the octonitrate of starch, but that will remove the hexanitrate. I have found a suitable agent for this purpose in a hot solution of ammonium hydrate. The nitro-starch powder should be treated with this solution for fifteen minutes or more.

By the process above described I produce a body having properties and a constitution different from those of any nitro-starch previously known to me. I find that this body contains about 16.5 per cent. of nitrogen, so that it would appear to be an octonitrate, the composition of which may be expressed either by the formula The reaction presumbly takes place according to the equation C12H20010+ I C12H12(NO2)8010+ This new compound has a chemical stability hitherto unapproached by any form of nitrostarch and is of vastly greater explosive force. The product detonates by the fulminate cap more perfectly than will nitroglycerin, even when the new nitro-starch is used in the proportion of ten per cent. in a dynamite mixture, the balance of which consists of sodium nitrate or similar oxidant and carbonaceous material. The explosive power of the new nitro-starch is at equal density about equal to that of nitroglycerin. The stability of the new nitro-starch is of great value in that it enables the product to be shipped and storedunder varying conditions of temperature and moisture. I

The product is insoluble in alcohol, ether, and dilute ammonium hydrate, hot or cold. It is soluble in ether alcohol and in acetic ether. When stabilized,'it is an orange-colored powder, silky to the touch, and having no crystalline nature. Its actual specific gravity is about 1.7; but its apparent specific gravity is about 1.2. It can be dissolved in concentrated sulfuric acid only with the greatest difliculty and difi'ers in this respect from nitrocellulose and the lower nitrates of starch. The usual Lunges nitrometer test is therefore not available for my compound, and instead of it I employ other methods of determining the percentage of nitrogen in the compound. For instance, a good method of making a nitrogen determination of this new product is that known as the Schultz-Tieman test.

The product is identified from a chemical standpoint by the determination of the nitro-. gen percentage and also the determination of the carbon percentage by a combustion test, these two determinations to show the constitution corresponding to the formula C12H12(NO2)8010- I have found that the new compound above described is formed when treating starch in the particular manner herein set forth, and I desire it to be understood that any substance which will yield the same product when subjected to said treatment is to be considered an equivalent of starch for the purpose of my invention and that the claims are to be interpreted as covering such equivalents.

hat I claim as-new, and desire to secure by Letters Patent, is

1. The process of highly nitrating starch,

which consists in maintaining the intimate copresence of dry starch, nitric acid and free sulfuric anhydrid throughout the period of nitration.

2. The process of making a highly-nitrated starch compound, which consists in preparing a mixture of nitric acid and sulfuric acid having an excess of free sulfuric anhydrid, forcibly introducing the finely-powdered starch below the surface of the mixture, and replenishing the supply of anhydrid to preserve an excess of free sulfuric anhydrid during the nitration process.

3. The process of making highly-nitrated starch compound, which consists in preparing a mixture of nitric acid and sulfuric acid having an excess of free sulfuric anhydrid, and

forcibly introducing the finely powdered starch below the surface of the mixture.

4%. The process of making a highly-nitrated starch compound, which consists in subjecting starch to the action of nitric acid and free sulfuric anhydrid, and replenishing the supply of anhydrid to preserve an excess of free sulfuric anhydrid during the nitration process, separating the excess of acids from the resulting nitrated product, washing said prod uct, and finally stabilizing it.

5. The process of making a highly-nitrated starch compound, which consists in subjecting starch to the action-of nitric acid and free sulfuric anhydrid, and replenishing the supply of anhydrid to preserve an excess of free sulfuric anhydrid during the nitration process, separating the excess of acids from the resulting nitrated product, washing said product, and finally stabilizing it by treatment with a hot solution of ammonium hydrate.

6. The process of making a highly-nitrated starch compound, which consists in subjecting starch to the action of nitric acid and free sulfuric anhydrid, separating the excess of acids from the resulting nitrated product, washing said product, and stabilizing it by treatment with ammonium hydrate.

7. The process of producing a highly-nitrated starch compound, which consists in subjecting starch to the action of nitric and sulfuric acids maintained of such strength as to produce a compound insoluble in a hot solution of ammonium hydrate and containing about sixteen and a half per cent. of nitrogen.

8. The process of producing a highly-nitrated starch compound, which consists in subjecting starch to the action of nitric and sulfuric acids of such concentration as to produce a compound containing about sixteen and a half per cent. of nitrogen, and maintaining the strength of the acid mixture at a practically constant point during the entire process of nitration.

In testimony whereofI have signed my nameto this specification in the presence of two subscrlbing wltnesses.

ARTHUR HOUGH.

Witnesses:

JOHN LOTKA, OTTO v. SCHRENK. 

